Don't 12V battery banks over 500 Ah become less attractive than a generator? The weight and complexity of charging large banks and the ability of a generator to run AC seems to favor generators instead of large battery banks.

Don't 12V battery banks over 500 Ah become less attractive than a generator? The weight and complexity of charging large banks and the ability of a generator to run AC seems to favor generators instead of large battery banks.

I'm not sure that makes any sense. Nobody wants to listen to a generator runnning all the time. The loads a boat uses are quite light compared to what even the tiniest generator puts out. It's really inefficient to run even a dinky 1Kw Honda noisemaker to service even 15A (180W) worth of house lights and refrigeration. Better to run the goddamnednoisybox to charge up your batteries in a couple of hours then enjoy the quiet.

We've got 720Ah @24V of LiFePO4 batteries. Works just fine with a 7Kw generator running every three days or so for about 5 hours. We can invert for all the AC we need.

I have over 1100 watts of solar, and over 1200 amp hours of battery
I mainly run my generator to make hot water for the shower. Even in the winter I am 90% sufficient in the summer there is no question

Don't 12V battery banks over 500 Ah become less attractive than a generator? The weight and complexity of charging large banks and the ability of a generator to run AC seems to favor generators instead of large battery banks.

"run AC"?

Do you mean run A/C (air conditioning) or run AC power? Big difference.

There is no complexity in charging large battery banks unless you have many small batteries comprising the bank. If you need to generate AC power for short periods of time, a quality inverter will do the job.

If you need to generate significant AC power over long periods of time, then a generator is usually the best option. But if you are wanting a generator in order to run A/C (air conditioning), just remember that A/C is called "generator eaters" for a reason. If you cannot keep your generator loaded up when it is running, it will have a short lifespan.

Power generation is the key, not battery capacity. It is either solar, portable gas gen, diesel gen or engine. I am still amazed at people who size their batteries to handle 4-5 cloudy days when you can easily run the engine Midway and be done with it.

The problem with batteries over 5-600 AHrs is that they are heavy and serve no need on a typical sailboat.

An inverter helps with short loads but if you use aircon, electric pressure cooker or electric heat, it is a non-starter. I agree with you that a small portable genny is much more useful than solar charging, discharging, heat, inverter fan noise and the other issues with high current applications. For a larger boat, a diesel genny.

Don't 12V battery banks over 500 Ah become less attractive than a generator? The weight and complexity of charging large banks and the ability of a generator to run AC seems to favor generators instead of large battery banks.

I don't look at generator and battery bank as an either/or proposition.

Our genset will run our aircons and electric cooktop, heat water, charge batteries... and when we power lighter loads, the batteries do fine, quietly... for a while.

Mine are quite feasible. 1,575 Ah over six L-16s deep cycle FLA batteries in series-parallel. Right under the mast with a set of companionway stairs over 'em. Charging is via wind (300w) and solar (135w x 4 on an arch) and, soon, a 250 A alternator for "equalization underway". Oh, and a couple of Honda 2000s should I experience a failure (or need to operate power tools ashore).

The point was to stay as much as possible in the high end of SOC (75% or over). That meant sizing for anticipated use (daily drawdown) and working within that "band". I do not want a typical below-decks genset, but portables ganged are fine, because I use those for other things. I do not wish to run the auxiliary diesel just to make power, but when I do run it, I want to get as high an acceptance rate as I can when doing runs like "motoring out to the three-mile limit for pump-outs".

A lot of my ideas come from homesteaders, who've basically solved these issues already. I realize that most production boats don't want to haul 320 kilos of batteries, but I have a custom pilothouse in steel (see picture to left). Putting the batteries in has actually stiffened the boat up. The only thing I would recommend is taking a full-systems approach, starting with an honest appraisal of how much power you need and the importance of shore-independence to you. Other decisions, like solar/wind capacity, charger/inverter selection, and even wiring and fuse sizing, proceed from that initial appraisal of what you'll be safe with in terms of minimums (keep the nav lights and radio working) and what you'll be happy with in terms of amenities (hot water, "movie night" and ice cubes after three days of cloudy and calm weather). https://alchemy2009.blogspot.ca/2016...wering-up.html